introductory openfoam from 17th to 21st february, 2014 ... · matteo bargiacchi...

Matteo [email protected]

“This offering is not approved or endorsed by OpenCFD Limited, the producer of the OpenFOAM software and owner of the OPENFOAM® and OpenCFD® trade marks.”

Introductory OpenFOAM® Course

From 17th to 21st February, 2014

Today’s lecture

1. Post-processing tools: paraFoam and Paraview, differences and basic commands;

2. How to export animations from Paraview;3. More on post-processing complex flow patterns;4. Python scripting in Paraview 4.1.


Acknowledgements

These slides and the tutorials presented are based upon personal experience, OpenFOAM® source code, OpenFOAM® user guide, OpenFOAM® programmer’s guide, and presentations from previous OpenFOAM® training sessions and OpenFOAM® workshops.

We gratefully acknowledge the following OpenFOAM® users for their consent to use their material:• Hrvoje Jasak. Wikki Ltd.• Hakan Nilsson. Department of Applied Mechanics, Chalmers University of

Technology.• Eric Paterson. Applied Research Laboratory Professor of Mechanical

Engineering, Pennsylvania State University.• Tommaso Lucchini. Department of Energy, Politecnico di Milano.• Rupert Fisch. Technische Universitaet Muenchen.


Today’s lecture




Paraview and paraFoam


● Paraview is a post-processing environment able to read and process a vast variety of formats.

● ParaFoam is a specific version of Paraview (3.14) able to directly read the output produced by OpenFOAM® without intermediate conversion

● The differences are few:- paraFoam is able to manage results from different processors without reconstruction- paraview needs the domain to be reconstructed (otherwise each single processor should be singly opened) and converted to a readable file format

reconstructParfoamToVTK

- paraview from version 4.1 onwards has a very instructive Start Trace-Stop Trace tool

A simple cavity 3D case


● Open the cavity simulation folder and runparaFoam

or

● Open the blended wing body simulation folder and runFoamToVTK

● Run paraview and import the *.vtk files

Hands-on session


● Open the Blended Wing Body simulation folder and runparaFoam

or



Group slices and plot a velocity profile


Show Mach threshold and streamlines


Hands-on session


In the course’s directory ($ptofc) you will find many tutorials (which are different from those that come with the OpenFOAM® installation), let us try to go through each one to understand and get functional using OpenFOAM®.

If you have a case of your own, let me know and I will try to do my best to help you to setup your case. But remember, the physics is yours.

Today’s lecture




Hands-on session


● Open the cylinder2D simulation folder and runparaFoam

or



Today’s lecture

1. Geometry and Mesh generation using Salome: a mixing elbow created inside the GUI;

2. Hands on to create a simple geometry inside the GUI;3. Learn how to program in python to create script for

Salome and automatize the pre-processing phase;4. Import 2D images and create 2D meshes for OpenFOAM®;

5. Import geometries and create a meshed domain of computation;




The Q-criterion was named after the second invariant of the velocity gradient tensor u by Hunt [1988] (see also Dubrief [2000])∇

Visualize flow patterns: The Q criterion

where

positive Q isosurfaces isolate areas where the strength of rotation overcomes the strain, thus making those surfaces eligible as vortex envelopes

Q-criterion and streamlines

Northrop YF17: iso-surfaces of Q=10^5 colored according to pressure and streamlines colored according to velocity magnitude

Q-criterion and streamlines

Open /Day2/paraview/yf17Run foamToVTK or directly run paraFoam

Launch paraview and open vtk files

Create a streamTracer filter with the parameters:

● Point source: (-3.55, 0.55, 0.55)● Number of Points: 20● Radius: 0.1

Create a Gradient Of Unstructured Data Set filter computing Vorticity and Q-criterion from the velocity field

Create a Contour filter with positive Q iso-surfaces (choose a value around 10'000)

The Calculator Filter

Let us calculate the Density field from Pressure and Temperature distributions.

Set a Calculator filter and define the following expression with the Result Array Name “density”:

p/(287.3*T)

Set another Calculator filter to check the post-processed field “density” against the calculated field “rho” with the following expression:

(density-rho)/rho

Today’s lecture




The Python Shell


The Python shell in paraview is a powerful plugin to automatize post-processing phases.

From version 4.0 onwards a Start Trace / Stop Trace utility is available

Unfortunately paraFoam (running on version 3.14) is not compatible with different versions. In order to use version 4.1 the environment variable should be cleaned in the following way:

● comment # source $HOME/OpenFOAM/OpenFOAM-2.2.x/etc/bashrc● Log Out and Log In again

Otherwise take advantage of the paraview module inside Salome 7.3.0

Trace an action and run a *.py script

From Tools menu click on Start Trace

DO ONE SIMPLE THING...

...and Stop Trace.

Understand the output visualized in a pop-up window and copy only the relevant snippets in your *.py script beginning with:

from paraview.simple import *

From Tools menu, click on Python Shell;Then Run Script ;

Thank you for your attention

Disclaimer


introductory openfoam from 17th to 21st february, 2014 ... · matteo bargiacchi...

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